A simple technique of ripple minimization for highly reflective fiber Bragg grating (FBG) is demonstrated by use of natural gaussian beam shape. After writing FBG by interference beam pattern of gaussian shape, an equalization of average refractive index is performed by means of post-exposure by non-interfering gaussian beam shifted in left and right directions relative to FBG center at distance equal to beam radius.

Two direct numerical methods of soving Gel'fand--Levitan--Marchenko equations are developed based on bordering procedure, hermiscity, Cholesky decomposistion, Toeplitz symmetry and piecewise-linear approximation. The proposed methods are shown to surpass the discrete layer peeling algorithm in accuracy and stability at high reflectance.

The 4-parametric family of exactly solvable profiles of the Bragg reflector is analyzed. The physical meaning of the parameter set is explained. The solution is proposed to use for approximation of the Gaussian envelope. The high quality of the approximation within the Bragg window is demonstrated numerically.

A Raman gain spectral profile has been measured in a phosphosilicate fiber at high pump and Stokes (signal) wave powers by a coherent anti-Stokes Raman scattering (CARS) technique. It has been shown that the profile saturates homogeneously. The main saturation mechanism is proved to be the pump depletion; i.e., the Raman gain coefficient _gR does not depend on the pump and signal wave power of several watts. The possible influence of stimulated Brillouin scattering and four-wave mixing is discussed. In addition, a transient regime of the CARS signal has been experimentally observed and theoretically explained.

Pump conditions optimization has been performed for one-stage EDFA with three-level forward pumping and quasi-twolevel backward pumping. The optimization allows to achieve low noise figure, high efficiency of pump power conversion and sufficiently wide and flat gain spectrum.

We present an analytical model based on a wave kinetic equations that describes RFL output spectrum. We have shown both theoretically and experimentally that the four-wave mixing (FWM) is the main broadening mechanism. Near the Stokes wave generation threshold the Stokes wave spectrum profile is defined by the nondegenerate FWM between Stokes wave and pump wave. High above the generation threshold, the quasi-degenerate FWM between different Stokes wave longitudinal modes plays the main role. The shape and power dependence of the intracavity Stokes wave spectrum is in a excellent quantitative agreement with model predictions.

The results of experimental research of internode beat stability in a three mirror diode laser at active mode-locking are reported. It was obtained that major factor has affected beat stability is detuning between microwave pumping oscillator and intermode frequency. It was observed that frequency pulling effect take place. The maximum value of intermode frequency stability is 5.92x10^-14 (average time 10 sec.) at stability ofpumping microwave oscillator equals to 4x10^-14.

The multiple pulse passive mode-locking with equidistantly arranged pulses in a laser cavity has been analyzed. Mechanisms resulting in such type of passive mode-locking have been studied. Among of them there are the additional weak active amplitude and phase modulations of the intracavity radiation, the additional inertial nonlinear refractive index and darkening absorber. The transient period for the realization ofthe harmonic passive mode-locking due to these mechanisms has been estimated.

The interaction of dissipative solitons in fiber laser with nonlinear losses due to nonlinear polarization rotation is studied by numerical simulation. Technique control of spectrum and amplitude of pulse wings allows effective management of the soliton interaction under long distance between pulses (considerably much more than pulse duration). The interaction can be attractive or repulsive. Moreover the sign of the interaction may depend on distance between pulses.

Mode-locking characteristic of hybrid soliton pulse source (HSPS) utilizing linearly chirped raised-cosine flat top apodized fiber Bragg grating (FBG) is investigated by using coupled-mode equations. It is found that the fundamental repetition frequency range of HSPS is significantly extended by using linearly chirped raised-cosine flat top apodized FBG instead of linearly chirped Gaussian apodized FBG. The range of repetition frequencies over which proper modelocking is obtained is 2-3.3 GHz with linearly chirped raised-cosine flat top apodized grating whereas this range is 2.1- 2.95 GHz with linearly chirped Gaussian apodized grating.

We present a new multi-parameter family of analytical soliton solutions for nonlinear three-wave resonant interactions. We show the amplitude, phase-front shapes and general properties of the solitons. The stability of these novel parametric solitons is simply related to the value of their common group velocity.

In this paper it was for the first time experimentally proven that chirp of pumping femtosecond pulses has considerable effect on the degree of coherence of short-wavelength part of super-continuum (SC) with strongly expressed soliton structures in its spectrum. At the same time the soliton component of super-continuum retains full coherence when the chirp of pumping radiation is varied. The broadest spectrum width of SC and the highest degree of coherence of the short-wavelength components of SC are achieved at small positive values of the chirp parameter. The noise-to signal ratio of SC was analyzed with the help of numerical simulation and it was found that at the optimal near-zero chirp value the degree of coherence of our SC is sufficient for metrology applications.

We present theoretical and experimental studies of both scalar and polarization or modal pump-divided parametric amplification in photonic crystal fibers. In the scalar case, we discuss broadband parametric amplification at telecom wavelengths near 1550 nm. With a pump-divided scattering process, we discuss the possibility of widely tunable frequency conversion and four-wave mixing gain at visible wavelengths. We confirmed the theory by experiments where intense, linearly polarized pump pulses at wavelengths ranging from 532 to 625 nm led to the spontaneous generation of modulation instability sidebands with frequency shifts ranging from 3 up to 63 THz. The observations were in good agreement the experimental characterization and theoretical modelling ofthe linear and nonlinear properties of the PCF.

The propagation of the solitary waves in the resonant birefringent amplifier with linear losses is considered. The birefringent optical linear medium contains two-level atoms with the upper state degenerated over projection of angular moment. It is assumed that population of resonance levels of atoms is inverted. The steady state pulse of polarized radiation that is vectonal generalization of the known π-pulse was analytically found. Numerical simulations demonstrate the formation dynamics solitary waves originated in birefringent amplifier.

Characteristics of low-threshold ZnSe-based room-temperature green semiconductor alsers are studied in detail as dependent on transverse size (h) of an active region. It is shown that the efficiency increases with increasing h, then passes through a maximum, and gradually falls down when h exceeds the cavity length L. The effect can be explained by taking into account the excitation of different transversal modes.

Experimental data and theoretical model concerning superradiant emission from the LaF₃ medium doped with impurity praseodymium ions are presented in cases of free medium and when the medium is placed into resonator. The spiky structure of superradiance is registered and studied. When the medium is placed inside a cavity, a new channel of energy removal by superradiance related to the cavity mode appears; the old noncavity channels are preserved. The duration of superradiance in each channel is decreased and the modulation arises. These peculiarities of superradiance induced by the presence of resonator are explained on the basis of the developed mean-field theory.

Regularities of the optical coherence transformation in three-level systems, resulting from instability development and superradiance, are considered. It is shown that the superradiance eliminates optical coherence on the adjacent optically allowed transitions and induces optical coherence on the optically forbidden transition. This, in turn, makes it possible to observe new effects of photon-echo type. In such a way the known cases of supperradiant emission from the LaF₃:Pr³⁺ medium admit the described phase memory effect.

The excitation of a thin layer of two-level permanent dipole moment atoms by ultimately short (less than field oscillation period) electromagnetic pulses (videopulse) is observed. The numerical analysis of matter equations free of rotating wave approximation and relaxation reveals a strong affect of local field and Stark effect on temporal behavior oftransmitted field. Specifically it is demonstrated that a dense film irradiated by videopulse emits a short response with a delay much longer even than the characteristic cooperative time of atom ensemble. It is supposed that the local field in the thin layer of permanent dipole atoms is able to re-pump the atomic subsystem. The close analogy to nonlinear pendulum motion is discussed.

Nowadays, all optical devices based on nonlinear effects acquire a great importance in optical communications systems and photonic processing. Particularly relevant are the devices that use low-level power pumping in the generation of those effects. These optical devices can be implemented by means of different structures and materials. One of the most significant structure, here described and presented, is the semiconductor semimagnetic microcavity, composed by a Fabry-Perot microcavity with a semiconductor semimagnetic material and a quantum well in the middle. Inside these media nonlinear effects such as four wave mixing and magneto-optical polarisation rotations can be observed and utilised for developing optical amplifiers, wavelength converters and nonlinear magneto-optical based devices. In order to reduce the pumping power needed for obtaining nonlinear effects new structures with different materials can be built. For instance, Fabry-Perot vertical microcavities, whispering gallery based microcavities or hybrid system of photonic crystal microcavities can improve their performance and so make possible a real implementation. A key point in the design of such micro-resonators is the election of the appropriate material inside. A study of the influence of several materials, with a high dispersion and able to provoke electromagnetically induced transparency is, also, presented. The changes of the quality factor of these nonlinear micro-resonators are analysed. Potential applications for optical computing are shown.

This PDF file contains the front matter associated with SPIE Proceedings Volume 6612, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.